Soranne not sure if this will help you but I just wanted to say that I had a very good, easy experience using a USB sound device.
– I used “mplayer” not gstreamer.
– I’m using a Plantronics USB audio in/out stick that came with a pair of their headphones (not sure what chip is inside)
– Use BeagleBone with latest 2012-6-18 Angstrom (+ opkg update/upgrade 's )
I literally was able to copy an mp3 file into my home directory, and use “mplayer mysong.mp3” and it played immediately with a text UI on the command line console. Worked first time, just like you’d want it to.